The present invention relates to a hydraulic manifold for controlling hydraulic fluid to a hydraulic actuator for holding a latch in position and which is maintained under pressure so that the latch is held positively in position. Leakage in valves and past pistons of double acting actuators is almost impossible to stop, and the present manifold will accommodate such leakage while maintaining differential pressure on the piston of the actuator.
Power actuators used in connection with various attachment devices have been known. U.S. Pat. No. 5,562,397 shows an electric power actuator for an attachment plate, wherein the actuator is connected between latch members and upon extension will move latches into a latching position. The latches are maintained in this position for reliable operation of the device.
When a hydraulic cylinder or actuator is used in place of the electric actuator, it is desirable to maintain a pressure on the base end, to avoid releasing the latches unintentionally. If pressure is maintained on one side of a piston of a double acting actuator, leakage to the low pressure side can occur in the valve block and across the piston, and the actuator can drift and get to a point where the pressures on opposite sides of the pistons are equalized.
Various locking cylinders for coupling attachments onto implements have been advanced in the past, and also leakage of hydraulic fluids in a seal assembly have been corrected. The present invention finds use where there is a hydraulic actuator which is to be maintained in a locked position with pressure on one side of the piston.
The present invention relates to a manifold for providing hydraulic fluid under pressure to a latching double acting actuator, which will accommodate leakage to a low pressure side of the piston and valve while pressure is maintained on the opposite side of the piston to insure that the actuator remains in the locking position. The leakage can occur across the control valve used as well as across the piston.
The manifold has a logic valve to provide a reduced flow to the latching actuator, and provides for different fluid pressures to opposite sides of the piston so a higher pressure can be used for releasing the latch members, which may require greater force, than the pressure used for locking the latch members.
One specific application is in a quick attachment for skid steer loaders, such as that using two wedge type latch bars that are operated with a power actuator that is connected between bell crank type operator handles. The handles can remain in place to provide an indication of the position of the latch bars without interfering with the double acting actuator operation.
The hydraulic manifold is preferably mounted directly in the outlet of the hydraulic pump used from the power source on a skid steer loader. In order to avoid draft or other problems caused by leakage from high pressure to low pressure regions when the base end of the actuator is under pressure, the hydraulic line connected from the valve to the rod end of the actuator, that is to the chamber on the rod side of the piston, is connected with a branch line or passage to drain or tank through an orifice that restricts the flow, so small volumes of oil from the rod end line will bleed back to drain. The orifice is small enough so the actuator can operate when the rod end is provided with flow under pressure when the valve is shifted to retract the rod.
The manifold provides for accommodating leakage when a double acting actuator is maintained under pressure on one end of the actuator and on one side of the piston while permitting a slow, low flow drain from the lines connected to the other side of the piston as may be necessary to accommodate leakage past the piston and valve from the pressure side.